Uv-active binding agent

ABSTRACT

The present invention relates to processes for preparing actinic-radiation-curable and/or dual-cure poly(meth)acrylates by preparing a poly(meth)acrylate containing hydroxy-functional side chains and transesterifying or esterifying the poly(meth)acrylate containing hydroxy-functional side chains with a (meth)acrylate or (meth)acrylic acid. The present invention further relates to the actinic-radiation-curable and/or dual-cure poly(meth)acrylates themselves and to the use of the actinic-radiation-curable and/or dual-cure poly(meth)acrylates in the preparation of dispersions or as a component in coating formulations and topcoats comprising at least one actinic-radiation-curable and/or dual-cure poly(meth)acrylate.

The invention relates to a process for preparing radiation-curableand/or dual-cure poly(meth)acrylates, to the poly(meth)acrylatesthemselves, to their use as a component in the preparation ofdispersions or as a component in coating formulations, to coatingformulations comprising the poly(meth)acrylates of the invention and toa process for preparing the coating formulations and their use.

UV-curable and dual-cure poly(meth)acrylates are of particular interestfor use in topcoats. Poly(meth)acrylates generally have excellentoutdoor weather stabilities. In conjunction with a UV curing technology,additional advantages are achievable. For example, the scratchresistance of the coating can be increased significantly, with anattendant improvement in coating performance. Particularly important,however, are improvements in application, in particular a very rapiddrying of the coating materials. This property is critical for rapidprocessing technologies.

In accordance with the prior art, UV-curable polyacrylates are reactedby copolymerizing glycidyl methacrylate followed by thermal reactionwith acrylic acid in the presence of a catalyst (DE-A 2 436 186, EP-A 0650 978). Disadvantages associated with this prior art mode ofpreparation are the attendant secondary reactions and deteriorations incolor. In view of the reaction conditions; particularly the hightemperatures, under which the reaction is carried out it is absolutelynecessary to use stabilizers in order to prevent the free-radicalpolymerization of the acrylic acid used.

A conventional acidic esterification of poly(meth)acrylates containinghydroxy-functional side chains with acrylic acid is not possible, sincein the course of such reaction the ester bonds of the poly(meth)acrylateare cleaved.

Known from the prior art is the functionalization of polymeric compoundswith (meth)acrylic acid and/or (meth)acrylic esters.

EP-A 0 999 230 and EP-A 0 999 229 relate to processes for preparing(meth)acrylic esters of hydroxy-functional siloxanes and/orpolyalkylene-modified siloxanes ('230) and also of polyoxyalkylenes('229) by esterification or transesterification of the siloxanes orpolyoxyalkylenes, respectively, with (meth)acrylic acid and/or(meth)acrylic esters in the presence of an enzyme. According to EP-A 0999 230 and EP-A 0 999 229, however, only the specific polymers referredto are reacted with (meth)acrylic acid and/or (meth)acrylic esters.There is no mention of a reaction of poly(meth)acrylates.

E. Marechal et al., Polymer Bulletin 26, 55 to 62 (1991) relates to thetransesterification of oligo(methacrylates) containing terminal estergroups with allyl alcohol in the presence of lipase. Transesterificationtakes place only at the terminal groups.

H. Ritter et al., Polymer Bulletin 21, 535 to 540 (1989) relates to thelipase catalyzed acetylation of methacrylic acid polymers containing OHgroups. The acetylation takes place in the presence of vinyl acetate.Reaction with vinyl acetate produces a very good leaving group, with thealdehyde formed being easily removable from the reaction mixture.Nevertheless, the reaction time amounts to 2 20 to 1 days.

H. Ritter et al., Makromol. Chem. 193, 323 to 328 (1992) relates to theenzymatically catalyzed acylation of OH-containing comblike methacrylicacid polymers with active esters, such as vinyl acetate, phenyl acetate,4-fluorophenyl acetate, and phenyl stearate. There is no mention of anesterification of the polymers with acrylates. The-reaction times of thereaction according to Ritter et al. are very long (2, 4 and 6 days).

The object of the present invention is to provide a gentle and selectiveprocess for preparing poly(meth)acrylates functionalized with(meth)acrylic acid and/or (meth)acrylates which is more variable thanthe known preparation process starting from glycidyl methacrylate, isable to start from less expensive starting substances, and allows agentler preparation, so that new kinds of poly(meth)acrylatessubstituted by (meth)acrylic groups are obtainable.

The object is achieved by a process for preparing UV-curable and/ordual-cure poly(meth)acrylates, comprising the following steps:

-   a) preparing a poly(meth)acrylate containing hydroxy-functional side    chains by polymerizing    -   aa) at least one (meth)acrylate of the general formula (I) as        component A    -   in which    -   R¹ is H, CH₃ or CH₂OH and    -   R² is an alkyl or cycloalkyl radical which is unsubstituted or        substituted by functional groups such as acrylic, ether, amino,        epoxy, halogen or sulfonic acid groups, preferably a C₁ to C₁₈        alkyl radical, more preferably a C₁ to C₈ alkyl radical, very        preferably a C₁ to C₈ alkyl radical unsubstituted by functional        groups, in particular a methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, 2-ethylhexyl, tert-butyl, cyclohexyl,        tert-butylcyclohexyl, isobornyl or trimethylcyclohexyl radical;        and    -   ab) at least one hydroxyalkyl (meth)acrylate of the general        formula (11) as component B    -   in which    -   R¹ is H, CH₃ or CH₂OH and    -   R³ is —(CH₂)_(n)—, —CH₂—CH(CH₃)—CH₂— or —CH₂CH(CH₃)— or        —CH(CH₃)CH₂— or    -   n is at least 2, preferably 2 to 8, more preferably 2 to 6, very        preferably 2 to 4,        -   the hydroxyalkyl (meth)acrylate of the general formula (II)            being selected in particular from the group consisting of            2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate            or hydroxybutyl (meth)acrylate; and    -   ac) if desired, further comonomers, copolymerizable with the        (meth)acrylates of the general formula (I) and (II), as        component C, preferably selected from the group consisting of        styrene, acrylonitrile, vinyl acetate, vinyl propionate, vinyl        chloride, vinylidene chloride, butadiene, and adducts of        Versatic acid glycide residues and unsaturated acids, especially        (meth)acrylic acid, and    -   ad) if desired, auxiliary monomers as component D preferably        selected from the group consisting of (meth)acrylic acid,        itaconic acid, maleic acid, fumaric acid, crotonic acid, and the        amides of said acids;-   and-   b) transesterifying or esterifying the poly(meth)acrylate containing    hydroxy-functional side chains with a (meth)acrylate or    (meth)acrylic acid, preferably with methyl, ethyl, 2-ethylhexyl or    butyl(meth)acrylate, in the presence if desired of stabilizers    selected from the group consisting of 2,6-dibutylphenols such as    di-tert-butylphenol, p-cresol, hydroquinone, dimethylhydroquinone,    phenothiazines and phosphorous esters, in the presence of an enzyme    which catalyzes the transesterification or esterification.

“(Meth)acrylic acid” is used as an abbreviation for “methacrylic acid oracrylic acid”; correspondingly, “(meth)acrylate” is used as anabbreviation for “methacylate or acrylate”.

The process of the invention enables functional groups, especially(meth)acrylic groups, to be introduced gently into poly(meth)acrylateswithout the likelihood of cleavage of the ester groups of thepoly(meth)acrylate. Moreover, it is possible to prepare thefunctionalized polymers starting from poly(meth)acrylates containinghydroxy-functional side chains, which are substantially less expensivethan glycidyl-functionalized poly(meth)acrylates used hitherto in theprior art.

Step a)

In a preferred embodiment of the process of the invention step a) iscarried out using

-   -   10 to 80% by weight, preferably 20 to 80% by weight, more        preferably 30 to 70% by weight of component A, and    -   10 to 80% by weight, preferably 20 to 70% by weight, more        preferably 20 to 60% by weight of component B, and    -   0 to 50% by weight, preferably 0 to 40% by weight, more        preferably 5 to 25% by weight of component C, and    -   0 to 15% by weight, preferably 0 to 10% by weight, more        preferably 0.5 to 5% by weight of component D.

The poly(meth)acrylates used in accordance with the invention,containing hydroxy-functional side chains, can be prepared by variousmethods known to the skilled worker. Preference is given to theirpreparation by free-radical polymerization.

The polymerization takes place in general by emulsion, solution or bulkpolymerization, preference being given to emulsion polymerization orsolution polymerization.

In one embodiment the poly(meth)acrylates containing hydroxy-functionalside chains are prepared by emulsion polymerization. In the case ofemulsion polymerization components A, B, and, where appropriate, C and,where appropriate, D are reacted with one another in the presence ofwater, emulsifiers, initiators, and, where appropriate, regulators.

Emulsifiers used are generally anionic, nonionic, cationic or amphotericemulsifiers, with anionic or nonionic emulsifiers being preferred.Suitable anionic emulsifiers are sodium, potassium or ammonium salts oflong-chain aliphatic carboxylic acids and sulfonic acids, alkali metalC₁₂₋₁₆ alkyl sulfates, oxethylated and sulfated or sulfonated long-chainaliphatic alcohols or alkylphenols, and sulfodicarboxylic esters.Suitable noninic emulsifiers are oxethylated fatty alcohols andalkylphenols, the ethylene oxide units possibly amounting to between 2and 50 mol/mol. Suitable cationic emulsifiers are ammonium, phosphonium,and sulfonium compounds including at least one long aliphatichydrocarbon chain as a hydrophobic moiety. It is also possible to use acombination of different emulsifiers: for example, ionic and nonionicemulsifiers.

The water used is preferably distilled or deionized, since salts mayaffect the stability of the emulsion. Generally speaking, thepolymerization process is carried out under nitrogen, since oxygeninhibits the polymerization.

The molecular weight of the poly(meth)acrylates containinghydroxy-functional side chains can be lowered by adding regulators.Suitable regulators are, for example, halogenated compounds such ascarbon tetrachloride, carbon tetrabromide, bromal, benzyl bromide, andtrichlorobromomethane, or mercaptans such as butyl mercaptan or dodecylmercaptan or Rongalit® C.

Suitable initiators are in general all initiators known to the skilledworker for polymerizing (meth)acrylates. Use is made in general ofwater-soluble peroxo compounds such as alkali metal or ammoniumpersulfate, hydrogen peroxide or tert-butyl peroxyethylhexanoate. Alsosuitable are redox systems such as H₂O₂-ascorbic acid,H₂O₂-Fe(II)/Fe(III), H₂O₂-Ce(IV), persulfites-Fe, metabisulfites-Fe orhydroperoxides-metal salts. The initiators are used generally in anamount of 0.05 to 8% by weight, preferably 0.2 to 2% by weight, based onamount of monomers used.

Any initiators still present after the polymerization can be deactivatedafter the polymerization in order to prevent possible polymerization ofthe poly-(meth)acrylates prepared in accordance with the invention instep b). The deactivation is generally accomplished by adding a reducingagent, e.g., ascorbic acid.

The polymerization is generally conducted within a temperature rangefrom 30 to 120° C., preferably 40 to 110° C., more preferably 50 to 90°C. The polymerization is generally conducted under a pressure of 1 to20, preferably 1 to 15 bar, more preferably 1 to 5 bar.

The emulsifiers are generally used in an amount of 0.5 to 15% by weight,preferably of 0.5 to 10% by weight, more preferably 0.5 to 5% by weight,based on the amount of components A, B, if desired, C, and, if desired,D that are used.

The particle diameter of the poly(meth)acrylates containinghydroxy-functional side chains that are obtained after polymerization isgenerally 20 to 1000 nm, preferably 20 to 500 nm, more preferably 50 to400 nm, determined by means of light scattering.

The pH during the emulsion polymerization is generally between 1 and 6,preferably between 2 and 6. The hydroxyl numbers are generally at least20 to 180, preferably at least 40 to 120. The solids content of thedispersions is generally 10 to 50, preferably 20 to 40, and the glasstransition temperature of the polymers obtained is generally between −40and +80° C.

The resultant poly(meth)acrylates containing hydroxy-functional sidechains generally have an average molecular weight of 1000 to 2 000 000,preferably 1000 to 1 000 000, more preferably 50 000 to 500 000. Theaverage molecular weight was determined by means of gel permeationchromatography (GPC). The molecular weight in question is thenumber-average molecular weight.

The poly(meth)acrylates containing hydroxy-functional side chains can beprepared by means of a one-pot or batch procedure, feed techniques, andcontinuous procedures. The conduct of said procedures is known to theskilled worker.

The poly(meth)acrylate containing hydroxy-functional side chains that isobtained in step a) can be isolated by methods known to the skilledworker. One embodiment is described, for example, in EP-A 0 029 637, butin the process according to the present specification hydroxyl-freesolvents are used, or in a second step a hydroxyl-containing solvent isreplaced by a hydroxyl-free solvent. For use in step b) of the processof the invention the poly(meth)acrylate containing hydroxy-functionalside chains, following its isolation, is used in water-free form.

In another preferred embodiment the poly(meth)acrylates containinghydroxy-functional side chains are prepared by solution polymerization.In the solution polymerization the components A, B, and, whereappropriate, C and, where appropriate, D are reacted with one another inthe presence of a solvent, initiator and, where appropriate, regulators.

Initiators suitable for the solution polymerization are peroxides suchas dialkyl peroxides, e.g., di-tert-butyl peroxide and di-tert-amylperoxide, peroxy esters such as tert-butyl peroxy-2-ethylhexanoate andtert-amyl peroxy-2-ethylhexanoate, diacyl peroxides such as benzoylperoxide, lauroyl peroxide, and decanoyl peroxide, percarbonates such astert-butyl peroxyisopropyl carbonate, di-2-ethylhexyl peroxydicarbonate,perketals and ketone peroxides, and also azo initiators such as2,2′-azobis(2,4-dimethylpentanenitrile),2,2′-azobis(2-methylpropanonitrile), 2,2′-azobis(2-methylbutanonitrile),1,1′-azobis(cyclohexanecarbonitrile),2,2′-azobis(2,4,4-trimethylpentane), and2-phenylazo-2,4-dimethyl4-methoxyvaleronitrile.

Preferred solvents are those not disruptive to an enzymatic reaction inaccordance with step b), so that removal of the solvent prior toexecution of step b) is unnecessary. Particular preference is given tosolvents selected from methyl isobutyl ketone, acetone, xylene,N-methylpyrrolidone, methyl ethyl ketone, methyl propyl ketone, methylamyl ketone, and solvent naphtha.

Step b)

In step b) the poly(meth)acrylate containing hydroxy-functional sidechains is transesterified or esterified with at least one (meth)acrylateor (meth)acrylic acid or a stabilizer in the presence of an enzyme whichcatalyzes the transesterification or esterification. Preference is givento carrying out a transesterification with methyl, ethyl, 2-ethylhexylor butyl (meth)acrylate.

The enzymatic transesterification or esterification with a(meth)acrylate or (meth)acrylic acid takes place in general at lowtemperatures, preferably 10 to 100° C., more preferably 20 to 80° C. Thereaction conditions during the enzymatic transesterification oresterification are mild. The low temperatures and other mild conditionsprevent the formation of-by-products-in step b), which may otherwiseoriginate, for example, from chemical catalysts or as a result ofunwanted free-radical polymerization of the (meth)acrylate used or ofthe (meth)acrylic acid used, which can otherwise be prevented only byadding stabilizers.

For the enzymatic reaction (step b)) the product from step a) can beused in general without further pretreatment. If required, the productmay be freed from volatiles (e.g., solvents) or additional substances(e.g., solvents) may be added. Specifically, it should as far aspossible be free from free-radical initiators or have a low free-radicalinitiator content.

Preferred enzymes used are hydrolases, especially hydrolases selectedfrom the group consisting of lipases, esterases, and proteases. Theenzymes can be used in free form or in immobilized form on a support towhich they have been chemically or physically bound. The amount of theenzyme catalyst is preferably 0.1 to 20% by weight, more preferably 1 to10% by weight, based on the poly(meth)acrylate containinghydroxy-functional side chains that is used.

The reaction time depends among other things on the amount used and onthe activity of the enzyme catalyst and the desired degree ofconversion, and also on the hydroxy-functional side chain of thepoly(meth)acrylate.

The (meth)acrylate used for the transesterification or the (meth)acrylicacid used for the esterification is generally employed in equimolaramounts or in excess in relation to the number of hydroxy-functionalside chains in the poly(meth)acrylate. Preference is given to using amolar ratio of (meth)acrylate or (meth)acrylic acid to hydroxy groups inthe side chains of the poly(meth)acrylate of 1:1 to 10:2. Higherexcesses are not disruptive.

Generally speaking, in step b), 20-100%, preferably 40 to 100%, morepreferably 60 to 100% of all hydroxy-functional side chains originallypresent in the poly(meth)acrylate are reacted with a (meth)acrylate or(meth)acrylic acid.

Suitable stabilizers, used where appropriate, are selected from thegroup consisting of 2,6-dibutylphenols such as di-tert-butylphenol,p-cresol, hydroquinone, dimethylhydroquinone, phenothiazines, andphosphorous esters. It is, however, also possible to carry out step b)without using stabilizers.

The reaction can be carried out-in all reactors suitable for such areaction. Reactors of this kind are known to the skilled worker. Thereaction takes place with preference in a stirred tank reactor, a fixedbed reactor or a Taylor reactor.

The alcohol formed or the water of reaction formed during thetransesterification or esterification can be removed by methods known tothe skilled worker: for example, by absorption (with molecular sieve,for example), distillation or pervaporation.

The reaction is continued until the desired conversion, generally 5 to100%, has been reached. In the case of a reaction regime withsimultaneous removal of the water or alcohol formed during the reactionit is possible to achieve higher conversions in shorter reaction timesowing to the shifting of the reaction equilibrium.

Following the reaction the enzyme catalyst can be separated off byappropriate measures, filtration or decanting for example, and can ifdesired be used a number of times.

A further subject of the present specification are UV-curable and/ordual-cure poly(meth)acrylates preparable by the process of theinvention. Owing to the mild reaction conditions in the process of theinvention it is possible to obtain new kinds of(meth)acryloyl-functional poly(meth)acrylates without the risk ofcleavage of the ester bonds in the poly(meth)acrylates by acid catalysisor high temperatures.

These (meth)acryloyl-functional poly(meth)acrylates of the invention aresuitable as binders in radiation-curable or dual-cure coating materials:for example, in topcoats such as transparent clearcoat materials, butalso in undercoat materials, primers, and surfacers. The(meth)acryloyl-functional poly(meth)acrylates have excellent weatherstability. In conjunction with a curing technology (radiation cure ordual cure) it is possible to obtain further advantages: for example, anincrease in the scratch resistance of a coating. Particularly decisive,however, is the improvement in application through use of the(meth)acryloyl-functional poly(meth)acrylates of the invention, sincethey allow rapid drying.

A further subject of the present specification is therefore the use ofthe (meth)acryloyl-functional poly(meth)acrylates of the invention or ofthose prepared by the process of the invention as binders inradiation-curable or dual-cure coating materials, preferably intopcoats, more preferably in transparent clearcoat materials.

By “dual-cure” is meant that the materials are curable thermally andwith actinic radiation. In the context of the present invention actinicradiation means electromagnetic radiation such as visible light, UVradiation or X-rays, especially UV radiation, and corpuscular radiationsuch as electron beams.

Radiation-curable binders are those curable by means of actinicradiation as defined above, in particular by means of UV radiation.

A further subject of the present specification are coating formulationscomprising the (meth)acryloyl-functional poly(meth)acrylates of theinvention or those preparable by the process of the invention. The(meth)acryloyl-functional poly(meth)acrylates or thestabilizer-functionalized poly(meth)acrylates can be used both inbasecoat materials and in topcoat materials. In view of their particularproperties such as the enhancement of scratch resistance in conjunctionwith high UV stability of a coating their use in topcoats is preferred.

Generally speaking, the composition of the topcoat is selected such thatthe cured topcoat material has a storage modulus E′ in therubber-elastic range of at least 10^(7.6) Pa, preferably of at least10^(8.0) Pa, more preferably of at least 10^(8.3) Pa, and a loss factorat 20° C. of not more than 1.10, preferably not more than 0.06, thestorage modulus E′ and the loss factor tanδ having been measured bydynamic-mechanical thermoanalysis on homogeneous free films with athickness of 40±10 μm. The loss factor tanδ is defined as the quotientof the loss modulus E″ and the storage modulus E′.

Dynamic-mechanical thermoanalysis is a general measurement method fordetermining the viscoelastic properties of coatings and is described,for example, in Murayama T., Dynamic Mechanical Analysis of PolymericMaterial, Elsevier, New York, 1978 and Loren W. Hill, Journal ofCoatings Technology, Vol. 64, No. 808, May 1992, pp. 31 to 33. Themeasurements can be carried out, for example, using the instruments II,MKIII, or MKIV from the company Rheometrics Scientific.

The radiation-curable or dual-cure topcoats preferably have a viscosityat 23° C. of < than 100 s efflux time in the DIN4 cup, more preferably<80 s efflux time in the DIN4 cup. For casting application and rollerapplication the viscosity may also be above this.

The topcoats of the invention comprise in addition to the(meth)acryloyl-functional poly(meth)acrylates of the invention, ifdesired, one or more photoinitiators and, if desired, customaryauxiliaries and additives. Suitable photoinitiators are customaryphotoinitiators used in radiation-curable or dual-cure coatingmaterials, examples being benzophenones, benzoins or benzoin ethers,preferably hydroxyacrylic ketones and bis(acyl)phosphine oxides. It isalso possible, for example, to use those in commerce under the nameIrgacure® 184, Irgacure® 1800, and Irgacure® 500 from Ciba Geigy,Genocure® MBF from Rahn, and Lucirin® TPO from BASF AG.

Suitable further auxiliaries and additives are, for example, lightstabilizers (for example HALS compounds, benzotriazoles, oxalanilid, etcetera), slip additives, polymerization inhibitors, flatting agents,defoamers, leveling agents, and film-forming auxiliaries, cellulosederivatives for example, et cetera. Additionally it is possible to userheology control components, such as organic urea compounds, urethaneurea compounds and/or SiO₂.

The topcoats of the invention are employed in particular as clearcoatmaterials, so that they normally contain no hiding pigments and nofillers, or only transparent fillers. Also possible, however, is theiruse in the form of pigmented topcoats. In that case the topcoatsadditionally comprise pigments. Furthermore, in this case the topcoatsmay comprise one or more fillers.

A further subject of the present application are therefore topcoatscomprising

5 to 80% by weight, preferably 10 to 60% by weight, more preferably 20to 50% by weight of at least one (meth)acryoyl-functionalpoly(meth)acrylate of the invention or one prepared by the process ofthe invention,

0.5 to 15% by weight, preferably 1 to 10% by weight, more preferably 1to 5% by weight of at least one photoinitiator,

0.5 to 8% by weight, preferably 1 to 6% by weight, more preferably 1 to4% by weight of further auxiliaries and additives,

0 to 40% by weight, preferably 0 to 30% by weight, more preferably 0 to25% by weight of pigments,

and 0 to 40% by weight, preferably 0 to 30% by weight, more preferably 0to 25% by weight of at least one filler, such as transparent metaloxides, BaSO₄, and waxes.

Preferred (meth)acryloyl-functional poly(meth)acrylates,photoinitiators, auxiliaries and additives, and fillers and pigmentshave already been specified above.

The topcoats of the invention are prepared by mixing the individualcomponents in accordance with methods known to the skilled worker inapparatus known according to the skilled worker.

A further subject of the present specification is therefore a processfor preparing the topcoat of the invention, in which the(meth)acryloyl-functional poly(meth)acrylate, the photoinitiator, ifdesired further auxiliaries and additives, and, if desired, fillers andpigments are mixed with one another.

The topcoats of the invention are generally applied to substrates coatedwith a basecoat material. They may be applied by what is known as coilcoating or by injection molding to the substrates. Such substrates are,for example, metal sheets, or metal strips and plastics of any kind,e.g., automobile bodies and motorcycle parts.

After the topcoat has been applied it is subjected to a radiation cureor dual cure. The equipment and conditions for these curing methods areknown from the literature and require no further description (forradiation curing see, for example, R. Holmers, UV and E. B. CuringFormulations for Printing Inks, Coatings and Paints, SITA Technology,Academic Press, London, United Kingdom 1984).

The examples which follow provide further illustration of the invention.

EXAMPLES

Formula: Initial Methyl isobutyl ketone 540.0 g charge Monomers Styrene10.00% by wt.¹⁾ 123.6 g EHA (2-ethylhexyl acrylate) HEMA 46.50% by wt.¹⁾574.4 g (hexylethyl methacrylate) HBA (hydroxybutyl acrylate) AA(acrylic acid) 27.00% by wt.¹⁾ 336.6 g 15.00% by wt.¹⁾ 185.2 g 1.50% bywt.¹⁾ 18.6 g rinse Methyl isobutyl ketone 5.0 g Initiator tert-Butyl 8%by wt.²⁾ 98.8 g peroxy-2-ethylhexanoate Methyl isobutyl ketone 74.2 grinse Methyl isobutyl ketone 46.6 g End 2000.0 g¹⁾based on the sum of the components styrene, EHA, HEMA, HBA, AA²⁾based on the sum of the components styrene, EHA, HEMA, HBA, AAProcedure:

Weigh out initial charge and heat to 110° C. At constant temperature,meter monomers and initiator into the reactor at a uniform rate. After 4hours the monomer feed is at an end. After 4.5 hours the initiator feedis at an end. After the end of the metering of initiator polymerizationis continued for 1 hour, followed by cooling and discharge of thereaction mixture obtained. *end values: Solids (1 h, 130° C.): 66.3% OHnumber (theoretical) total: 174.8 mg/g (determined to DIN 43402) OHnumber (practical): 165 mg/g (determined to DIN 53246) GC (residualmonomer content)³⁾: EHA 0.3%; AA < 0.3% all others < 0.1% GPC⁴⁾ M_(n) ⁵⁾5829 M_(w) ⁶⁾ 20 722 M_(w)/M_(n) ⁷⁾ 3.55³⁾GC = gas chromatography⁴⁾GPC = gel permeation chromatography (with polystyrene standard)⁵⁾M_(n) = number-average molecular weight⁶⁾M_(w) = weight-average molecular weight⁷⁾M_(w)/M_(n) = polydispersity2. Preparation of a UV-Active Polyacrylate

Batch: 300 ml of polymer solution in methyl isobutyl ketone from Example1

-   -   300 g of methyl acrylate (MA)    -   150 mg of methoxyphenol    -   150 g of 5 Å mole sieve    -   30 g of Novozym® 435 (immobilized lipase from Candida antarctica        from the company Novozymes)

The components stated are stirred at 40° C. for 72 hours. The reactionmixture is subsequently filtered and the polyacrylate obtained is washedwith methyl isobutyl ketone (MIK). The excess MA and MIK is removed invacuo on a rotary evaporator at 60° C. to 70° C. This gave 227 g oftarget product. The fraction of the acrylated hydroxy groups wasdetermined as being about 34% by means of the OH number.

The OH number was determined in accordance with a method which is knownin the prior art (DIN 53240, Part 2).

3. Preparation of a UV Coating Formulation a) Stock varnish inventive UVpolyacrylate 32.5 Sartomer ® 399 30.6 Thixharz ® SCA 11.5 (basis:benzylamine/hexamethylene diisocyanate) Irgacure ® 184 (photoinitiator)0.8 Lucirin ® TPO (photoinitiator) 0.4 Byk ® 358 (leveling assistant)0.2 Tinuvin ® 292 (free-radical scavenger) 1.0 Tinuvin ® 400 (UVabsorber) 1.0 Butyl acetate 22.0

A curing agent mixture composed of 72.7 parts of Roskydal® UA VP LS 2337(unsaturated isophorone diisocyanate), 18.2 parts of Roskydal® UA VP FWO3003 77 and 9.1 parts of butyl acetate is added (the parts are parts byweight).

The components were mixed with a dissolver.

4. The Coating Formulation was Applied by Spray Application.

5. Variation of the hydroxy-Functional Units

As the following examples show, different hydroxy-functional units canbe used. The examples mentioned are not, however, intended to be anyrestriction. The polymer solutions were prepared by methodscorresponding to Example 1.

10 g of polymer solution, 10 g of methyl acrylate, 5 g of mole sieve (5Å) and 1 g of immobilized lipase (Novozym® 435) were shaken at 40° C.for 72 hours. After filtration and concentration, the conversion wasdetermined by way of the OH number. Conversion Polymer solutionEsterified unit [%] 2 Hydroxyethyl acrylate 34 3 Hydroxyethyl acrylate41 4 Hydroxyethyl methacrylate 12 5 Hydroxyethyl methacrylate 22 6Hydroxyethyl methacrylate 47 7 Hydroxybutyl acrylate 67 8 Hydroxybutylacrylate 806. Reaction Optimization

It was possible to optimize the reaction conditions by varying thereaction time, the added amount of methyl acrylate, and mole sieve. Thepolymer solutions shown in the table under Example 5 were reacted underthe following optimized reaction conditions.

10 g of polymer solution, 2 g of methacrylate, 2 g of mole sieve and 1 gof Novozym® 435 were shaken at 40° C. for 24 hours. After filtration andconcentration, the conversion was determined by way of the OH number.Polymer solution Conversion [%] 2 23 3 39 5 6 6 17 7 40 8 46

1. A process for preparing poly(meth)acrylates curable with at least oneof actinic radiation or dual-cure utilizing actinic radiation andthermal cure, comprising the following steps: a) preparing apoly(meth)acrylate containing hydroxy-functional side chains bypolymerizing aa) at least one (meth)acrylate of the general formula (I)as component A

in which R¹ is H, CH₃ or CH₂OH and R² is an alkyl radical which isunsubstituted or substituted by functional groups such as acrylic,ether, amino, epoxy, halogen or sulfonic acid groups, and ab) at leastone hydroxyalkyl (meth)acrylate of the general formula (II) as componentB

in which R¹ is H, CH₃ or CH₂OH and R³ is —(CH₂)_(n)—, —CH₂—CH(CH₃)—CH₂—or —CH₂CH(CH₃)— or —CH(CH₃)CH₂— or

n is at least 2, and ac) if desired, further comonomers, copolymerizablewith the (meth)acrylates of the general formula (I) and (II), ascomponent C, and ad) if desired, auxiliary monomers as component D; andb) transesterifying or esterifying the poly(meth)acrylate containinghydroxy-functional side chains with a (meth)acrylate or (meth)acrylicacid in the presence of an enzyme which catalyzes thetrans-esterification or esterification.
 2. A process as claimed in claim1, wherein step a) is carried out using 10 to 80% by weight of componentA, 10 to 80% by weight of component B, 0 to 50% by weight of componentC, and 0 to 15% by weight of component D.
 3. A process as claimed inclaim 1, wherein enzymes used in step b) are hydrolases selected fromthe group consisting of lipases, esterases, and proteases.
 4. A processas claimed in claim 1, wherein step b) is carried out using methyl,ethyl, 2-ethylhexyl or butyl(meth)acrylate.
 5. A process as claimed inclaim 1, wherein the temperature at which step b) is conducted is 20 to100° C.
 6. A process as claimed in claim 1, wherein component B isselected from the group consisting of 2-hydroxyethyl(meth)acrylate,2-hydroxypropyl(meth)acrylate, and hydroxybutyl(meth)acrylate.
 7. Aprocess as claimed in claim 1, wherein 5 to 100% of the side chains ofthe poly(meth)acrylate prepared in accordance with step a) have been(meth)acrylated.
 8. Poly(meth)acrylates preparable prepared by a processas claimed in claim
 1. 9. (canceled)
 10. A topcoat containing 5 to 80%by weight of at least one poly(meth)acrylate prepared according to claim1 comprising 0.5 to 15% by weight of at least one photoinitiator, 0.5 to8% by weight of further auxiliaries and additives, 0 to 40% by weight ofpigments, and 0 to 40% by weight of at least one filler.
 11. A processfor preparing a coating formulation as claimed in claim 10, in which theindividual components are mixed with one another.
 12. (canceled)
 13. Adispersion comprising the poly(meth) acrylate of claim
 8. 14. A coatingcomposition comprising the the poly(meth)acrylate of claim
 8. 15. Acoating composition comprising the poly(meth)acrylate of claim 8selected from primers, surfacers and topcoats.
 16. A topcoatingcomposition comprising the the poly(meth)acrylate of claim
 8. 17. Atransparent clearcoat composition comprising the poly(meth)acrylate ofclaim
 8. 18. A process for preparing dispersions or coating formulationscomprising the step of adding poly(meth)acrylates curable with actinicradiation or both actinic radiation and thermal cure as claimed in claim8 as binders to dispersions or coating formulations.